voc
Hide rooms on overview page while preview image fails to load
This fixes the automatic update of preview/teaser images on the overview page (in the first commit) and also hides/shows rooms on the overview page depending on successful loading of the preview image, assuming that a stream is 'live' when the preview image can be loaded.
The change was inspired by a suggestion from @saerdnaer in the #voc-lounge, where I missed the part about fixing this on media.ccc.de at first and implemented it for the streaming website instead, which has a somewhat similar issue - and where implementing this is probably a bit easier. I'm not sure it's a good idea though to do this on the overview page, as it renders rooms where loading of the preview image fails 'inaccessible', so I don't mind if this PR gets discarded.
I've given the idea with the button a try, rebased everything on the current master and force-pushed this today. Each group now gets a button which allows to toggle the display of rooms with inactive streams.